Under Stress

Lock-in Thermography in Thermal Stress Analysis (TSA)

If you wish to clarify whether components have the required material characteristics for your application, you can make use of thermal stress analysis (TSA). In this process, external forces work cyclically on the test specimen, which causes change in the specimen’s mechanical stresses, which goes along with minor temperature changes. These temperature changes on the surface of the test specimen are made visible with the thermography camera and permit conclusions about areas with stress concentrations or weak points in which failure under constant load is expected.

Examination at Maximum Speed

For such analyses, for example, an Al sample is clamped into a resonance testing machine and stretched periodically in the elastic range. A high-resolution high-speed camera of the type ImageIR® 8300 hp continuously records the surface temperature of the sample. The camera detector (native format 640 × 512 IR pixels) is operated in sub-frame mode (320 × 256 IR pixels) with an image frequency of 600 Hz required due to the high temperature conductivity of Al. The data is captured with the software IRBIS® 3 online and then analysed with the software IRBIS® 3 active.

The results show that active thermography is suitable for qualitative tension measurement, both for the elastic stretch range and in the transition to the plastic stretch range. With the help of relevant formulas for the connection between changes in temperature and tension, the quantitative tension values can be calculated from temperature measurement values and material parameters.